We have investigated the effects on plant development of mutations in the Arabidopsis thaliana CLAVATA1 gene. In clavata1 plants, vegetative, inflorescence and floral meristems are all enlarged relative to wild type. The apical meristem can fasciate in the more severe mutant alleles, and this fasciation can occur prior to the transition to flowering. Flowers of clavata1 plants can have increased numbers of organs in all four whorls, and can also have additional whorls not present in wild-type flowers. Double mutant combinations of clavata1 with agamous, apetala2, apetala3 and pistillata indicate that CLAVATA1 controls the underlying floral meristem structure upon which these homeotic genes act. Double mutant combinations of clavata1 with apetala1 and leafy indicate CLAVATA1 plays a role in establishing and maintaining floral meristem identity, in addition to its role in controlling meristem size. In support of this, RNA expression patterns of AGAMOUS and APETALA1 are altered in clavata1 flowers.

REFERENCES

Bowman
J. L.
,
Smyth
D. R.
,
Meyerowitz
E. M.
(
1989
).
Genes directing flower development in Arabidopsis.
Plant Cell
1
,
37
52
Bowman
J. L.
,
Smyth
D. R.
,
Meyerowitz
E. M.
(
1991
).
Genetic interactions among floral homeotic genes of Arabidopsis.
Development
112
,
1
20
Coen
E. S.
,
Meyerowitz
E. M.
(
1991
).
The war of the whorls: genetic interactions controlling flower development.
Nature
353
,
31
37
Drews
G. N.
,
Bowman
J. L.
,
Meyerowitz
E. M.
(
1991
).
Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product.
Cell
65
,
991
1002
Goto
N.
,
Kumagai
T.
,
Koornneef
M.
(
1991
).
Flowering responses to light-breaks in photomorphogenic mutants of Arabidopsis thaliana, a long day plant.
Physiol. Plant
83
,
209
215
Huala
E.
,
Sussex
I. M.
(
1992
).
LEAFY interacts with floral homeotic genes to regulate Arabidopsis floral development.
Plant Cell
4
,
901
913
Irish
V. F.
,
Sussex
I. M.
(
1990
).
Function of the apetala-1 gene during Arabidopsis floral development.
Plant Cell
2
,
741
751
Jack
T.
,
Brockman
L. L.
,
Meyerowitz
E. M.
(
1992
).
The homeotic gene APETALA3 of Arabidopsisthaliana encodes a MADS box and is expressed in petals and stamens.
Cell
68
,
683
697
Koornneef
M.
,
van Eden
J.
,
Hanhart
C. J.
,
Stam
P.
,
Braaaksma
F. J.
,
Feenstra
W. J.
(
1983
).
Linkage map of Arabidopsisthaliana.
J. Hered
74
,
265
272
Leyser
H. M. O.
,
Furner
I. J.
(
1992
).
Characterization of three shoot apical meristem mutants of Arabidopsis thaliana.
Development
116
,
397
403
Mandel
M. A.
,
Gustafson-Brown
C.
,
Savidge
B.
,
Yanofsky
M. F.
(
1992
).
Molecular characterization of the Arabidopsis floral homeotic gene APETALA1.
Nature
360
,
273
277
Medford
J. I.
,
Behringer
F. J.
,
Callos
J. D.
,
Feldmann
K. A.
(
1992
).
Normal and abnormal development in the Arabidopsis vegetative shoot apex.
Plant Cell
4
,
631
643
Mertens
T. R.
,
Burdick
A. B.
(
1954
).
The morphology, anatomy and genetics of a stem fasciation in Lycopersicon esculentum.
Amer. J. Bot
41
,
726
732
Meyerowitz
E. M.
,
Bowman
J. L.
,
Brockman
L. L.
,
Drews
G. N.
,
Jack
T.
,
Sieburth
L. E.
,
Weigel
D.
(
1991
).
A genetic and molecular model for flower development in Arabidopsis thaliana.
Development
1
,
157
167
Miksche
J. P.
,
Brown
J. A. M.
(
1965
).
Development of vegetative and floral meristems of Arabidopsis thaliana.
Am. J. Bot
52
,
533
537
Reed
J. W.
,
Nagpal
P.
,
Poole
D. S.
,
Furuya
M.
,
Chory
J.
(
1993
).
Mutations in the gene for the red/far-red light receptor phytochrome B alter cell elongation and physiological responses throughout Arabidopsis development.
Plant Cell
5
,
147
157
Satina
S.
,
Blakeslee
A. F.
,
Avery
A. G.
(
1940
).
Demonstration of the three germ layers in the shoot apex of Datura by means of induced polyploidy in periclinal chimeras.
Am. J. Bot
27
,
895
905
Schultz
E. A.
,
Haughn
G. W.
(
1991
).
LEAFY, a homeotic gene that regulates inflorescence development in Arabidopsis.
Plant Cell
3
,
771
781
Smyth
D. R.
,
Bowman
J. L.
,
Meyerowitz
E. M.
(
1990
).
Early flower development in Arabidopsis.
Plant Cell
2
,
755
767
Szymkowiak
E. J.
,
Sussex
I. M.
(
1992
).
The internal meristem layer (L3) determines floral meristem size and carpel number in tomato periclinal chimeras.
Plant Cell
4
,
1089
1100
Vaughn
J. G.
(
1952
).
Structure of the angiosperm apex.
Nature
169
,
458
459
Vaughn
J. G.
,
Jones
F. R.
(
1953
).
Structure of the angiosperm inflorescence apex.
Nature
171
,
751
752
Weigel
D.
,
Alvarez
J.
,
Smyth
D. R.
,
Yanofsky
M. F.
,
Meyerowitz
E. M.
(
1992
).
LEAFY controls floral meristem identity in Arabidopsis.
Cell
69
,
843
859
Yanofsky
M. F.
,
Ma
H.
,
Bowman
J. B.
,
Drews
G. N.
,
Feldmann
K. A.
,
Meyerowitz
E. M.
(
1990
).
The protein encoded by the Arabidopsis homeotic gene AGAMOUS resembles transcription factors.
Nature
346
,
35
39
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